Issue #19512, #19515: remove shared identifiers, move identifiers where they
are used.

Move also _Py_IDENTIFIER() defintions to the top in modified files to remove
identifiers duplicated in the same file.
diff --git a/Python/import.c b/Python/import.c
index aea29e2..c96106f 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -310,7 +310,7 @@
 
     /* XXX Perhaps these precautions are obsolete. Who knows? */
 
-    value = _PyDict_GetItemId(modules, &_PyId_builtins);
+    value = PyDict_GetItemString(modules, "builtins");
     if (value != NULL && PyModule_Check(value)) {
         dict = PyModule_GetDict(value);
         if (Py_VerboseFlag)